1. Field of the Invention
The present invention is directed to photodynamic therapy using an illuminator that provides a uniform distribution of visible light. In particular, the present invention is directed to an apparatus and method for photodynamic treatment (PDT) or diagnosis (PD) of actinic keratosis of the scalp or facial areas of a patient. The present invention is also directed to an apparatus and method for PDT and PD of other indications (e.g., acne) and other areas of the patient (e.g., arms, legs, etc.).
As they are used here, the term xe2x80x9cvisible lightxe2x80x9d refers to radiant energy in the visible range of the electromagnetic radiation spectrum, and the term xe2x80x9clightxe2x80x9d refers to radiant energy including the ultraviolet (UV), infrared (IR) and visible ranges of the electromagnetic radiation spectrum.
2. Description of Related Art
Photodynamic therapy or photochemotherapy is currently being proposed to treat several types of ailments in or near the skin or other tissues, such as those in a body cavity. For example, PDT is being proposed to treat different types of skin cancer and pre-cancerous conditions. In PDT, a patient is administered a photoactivatable agent or precursor of a photoactivatable agent which accumulates in the tissue being diagnosed or treated. An area of the patient which includes the tissue being diagnosed or treated is then exposed to visible light. The visible light causes chemical and/or biological changes in the photoactivatable agent which in turn selectively locate, destroy or alter the target tissue while at the same time causing only mild and reversible damage to other tissues in the treatment area.
General background information on PDT using 5-aminolevulinic acid (xe2x80x9cALAxe2x80x9d) as the precursor of a photoactivatable agent can be found in U.S. Pat. No. 5,079,262, entitled xe2x80x9cMethod of Detection and Treatment of Malignant and Non-Malignant Lesions Utilizing 5-Aminolevulinic Acid,xe2x80x9d issued to James C. Kennedy et al. on Jan. 7, 1992, and U.S. Pat. No. 5,211,938, entitled xe2x80x9cMethod of Detection of Malignant and Non-Malignant Lesions by Photochemotherapy of Protoporphyrin IX Precursors,xe2x80x9d issued to James C. Kennedy et al. on May 18, 1993. The contents of these patents are incorporated herein by reference. The publication of James C. Kennedy et al. in the Journal of Clinical Laser Medicine and Surgery on Nov. 5, 1996, entitled xe2x80x9cPhotodynamic Therapy (PDT) and Photodiagnosis (PD) Using Endogenous Photosensitization Induced by 5-Aminolevulinic Acid (ALA): Mechanisms and Clinical Results,xe2x80x9d is also incorporated herein by reference. The xe2x80x9cFirst Phase IIIxe2x80x9d 1996 Annual Report by DUSA Pharmaceuticals, Inc. (Tarrytown, N.Y.) contains pictures and examples of use of the invention, and is also incorporated herein by reference.
As they are used here, the terms ALA or 5-aminolevulinic acid refer to ALA itself, precursors thereof and pharmaceutically acceptable salts of the same.
Most conventional, non-laser light sources are comprised of just three basic functional blocks: an emission source to generate photons (e.g., a light bulb); coupling elements to direct, filter or otherwise conduct the emitted light so that it arrives at the intended target in a usable form; and a control system to start and stop the production of light when necessary. The common office fluorescent lighting fixture is a good example of such a system. In these fixtures, white visible light is produced by a controlled mercury arc discharge which excites inorganic phosphor materials inside a glass tube. Energy transfer from the arc causes visible white light emission from the tube. The emitted visible light is directed toward the work space by reflectors in the lamp housing; the distribution of visible light to the target is often further increased by using a diffusing system. In the typical office setting, visible light production is controlled by a simple snap switch which interrupts the flow of power to the lamp.
For therapeutic reasons it is desirable to have a power output which is uniform in intensity and color. In particular, it is highly desirable to have an illuminator with a spectral output that overlaps to a large extent with the optical activation spectrum of the target photosensitizer. According to one preferred embodiment of the present invention, blue light having wavelengths exceeding 400 nm (nanometers) is particularly advantageous for certain diagnostic purposes and treatments, especially when ALA is the photoactivatable agent used for PD and PDT of actinic keratosis. However, visible light in other ranges of the spectrum, particularly in the green and red ranges between 400 and 700 nm, may also be used.
Conventional illuminators do not produce visible light that is sufficiently uniform in intensity over a contoured surface.
It is an object of the present invention, therefore, to provide an improved illuminator for PDT and/or PD.
Another object of the invention is to provide an illuminator for PDT that produces visible light of consistent uniformity in terms of both spectral characteristics and intensity over a diversely contoured surface. As it is used here, the term contoured surface refers to a non-planar surface.
Yet another object of the invention is to provide an illuminator for PDT or PD which produces visible light almost entirely in a selected wavelength range.
A further object of the present invention is to provide an illuminator for irradiating the face or scalp of a patient.
Yet a further object of the present invention is to provide a cooling system for improving the irradiance uniformity of an illuminator.
An additional object of the present invention is to provide an illuminator comprising a finite emitter that approximates the uniform output of an infinite plane emitter by varying the spacing of individual light sources within the illuminator.
Yet an additional object of the present invention is to provide a monitoring system for an illuminator comprising a single visible light sensor monitoring the visible light output of a plurality of light sources and outputting a signal to adjust the visible light output from the plurality light sources.
In accomplishing the foregoing objects, there has been provided according to the present invention an illuminator for PDT or PD of a contoured surface. The illuminator comprises a plurality of light sources generally conforming to the contoured surface and irradiating the contoured surface with substantially uniform intensity visible light, and a housing supporting the plurality of light sources with respect to the contoured surface.
In accomplishing the foregoing objects, there is also provided according to the present invention a method of PDT or PD of a contoured surface. The method comprises topically applying 5-aminolevulinic acid to the contoured surface, and irradiating the contoured surface with substantially uniform intensity visible light from a plurality of light sources generally conforming to the contoured surface.
In accomplishing the foregoing objects, there is also provided according to the present invention a cooling system for an illuminator including an elongated light source having a generally arcuate segment connected to a generally straight segment. The cooling system comprises a plenum enclosing the light source; an intake vent to the plenum receiving ambient air, the intake vent being positioned proximate a free end of the generally straight segment; and an exhaust vent from the plenum discharging heated ambient air, the exhaust vent being positioned proximate a connection between the generally arcuate and straight segments. The generally straight segment and a connection between the generally arcuate and straight segments receives greater cooling relative to the generally arcuate segment.
In accomplishing the foregoing objects, there is also provided according to the present invention a method of providing substantially uniform intensity light from an elongated light source having a generally arcuate segment connected to a generally straight segment. The method comprises providing greater cooling to the generally straight segment relative to the generally arcuate segment.
In accomplishing the foregoing objects, there is also provided according to the present invention an illuminator for emulating an infinite plane emitter. The illuminator comprises an emitting area having a perimeter, and a plurality of light sources being generally parallel to one another, said plurality of light sources being adapted for irradiating substantially uniform intensity light from said emitting area. Lateral spacing between adjacent ones of said plurality of light sources varies with respect to said perimeter.
In accomplishing the foregoing objects, there is also provided according to the present invention a monitoring system for an illuminator irradiating a surface. The monitoring system comprises a plurality of adjustable light sources adapted for irradiating the surface with substantially uniform intensity light; a light sensor being supported with respect to the plurality of light sources; a partition interposed between the light sensor and the plurality of light sources; a first aperture in the partition adapted for admitting light from a first one of the plurality of light sources to the light sensor, the first aperture being spaced from the light sensor a first distance and having a first cross-sectional area; and a second aperture in the partition adapted for admitting light from a second one of the plurality of light sources to the light sensor, the second aperture being spaced from the light sensor a second distance and having a second cross-sectional area. A ratio of the first and second cross-sectional areas is proportional to inverse squares of the first and second distances; and the light sensor is adapted for monitoring light output from the first and second ones of the plurality of light sources and outputting a signal to adjust light output from the plurality of light sources so as to provide the substantially uniform intensity light irradiating the surface.
In accomplishing the foregoing objects, there is also provided according to the present invention light for photodynamically diagnosing or treating a contoured surface, the light coming from a plurality of sources generally conforming to the contoured surface and irradiating the contoured surface with uniform intensity.
The present invention relies on similar fundamentals to that of the office fluorescent lighting system described above. According to an embodiment of the present invention: visible light is produced by contour surface conforming fluorescent tubes and their associated control electronics; visible light output from these tubes is directed toward the diagnosis or treatment area by the contour surface conforming shape of the tubes and other elements such as a reflector; and activation of the fluorescent tubes and visible light exposure on the contoured surface is controlled by the electronic circuitry.
The present invention differs from conventional light sources because of the biological requirements imposed on a PDT light source. A much higher degree of precision and integration is required for the components of the present invention. Output spectrum, irradiance, and irradiance uniformity all must be controlled to assure that the properties of the device are suitable to deliver light to the target lesions and drive the photodynamic reaction. To achieve this, each functional block within the present invention comprises carefully selected and engineered components. The principles of operation of each are described in detail below.
The inverse square law of optics states that the intensity of light from a point source received by an object is inversely proportional to the square of the distance from the source. Because of this behavior, distance from the source is an important variable in all optical systems. Thus, in order to achieve uniform facial or scalp irradiation, variations in output irradiance with distance must be minimized. A flat emitting surface would not deliver a uniform light dose to all contours of the face simultaneously because the non-planar facial and scalp surfaces could not be placed at a constant distance from the emitting surface. To ameliorate this problem, the present invention uses a U-shaped emitting surface that more closely follows the contours of the human face and scalp, and minimizes lamp to target distance variations which in turn minimizes irradiance variations at the target.
Since the output of tubular light sources may vary with temperature, temperature distribution also plays a key role in irradiance uniformity. Further, since the tube output may vary over its length, modulation of the temperature distribution may be used to control irradiance uniformity of the illuminator.
Additional objects, features and advantages of the invention will be set forth in the description which follows, and in part will be clear from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out in the appended claims.